This invention relates to the field of intravascular catheters, and more particularly to an inflatable member formed in part of liquid crystal polymeric material.
Balloon catheters generally comprise a catheter shaft with a inflatable member on the distal end of the shaft, and are used in a number of procedures, such as percutaneous transluminal coronary angioplasty (PTCA). In PTCA the balloon catheter is used to restore free flow in a clogged coronary vessel. The catheter is maneuvered through the patient's tortuous anatomy and into the patient's coronary anatomy until the inflatable member is properly positioned across the stenosis to be dilated. Once properly positioned, the inflatable member is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 4 atm) to reopen the coronary passageway.
The material used to make the catheter inflatable member must have sufficient strength to contain the inflation fluid without bursting. In addition, the degree of compliance must be tailored so that the inflatable member expands during use, but does not overexpand and damage the body lumen. During extrusion and subsequent processing of polymeric inflatable member tubing, the longitudinal and radial orientation of polymeric molecules can be tailored to increase the longitudinal and radial strength of the inflatable member produced therefrom. Because the force required to blow a inflatable member from tubing destroys some of the longitudinal orientation produced during extrusion, the extrusion process, and particularly the draw down ratio, is designed around optimizing the molecular orientation that is ultimately produced in the finished inflatable member. The strength of a inflatable member is typically expressed in terms of hoop strength and burst pressure.
Inflatable members formed from thermoplastics such as PET blended with liquid crystal polymers to improve the compliance of the inflatable member have been suggested (U.S. Pat. No. 5,306,246 (Sahatjian et al.)). However, Sahatjian et al. fails to address the problem of lower burst pressures of inflatable members produced from blends of a minor amount of liquid crystal polymer with a major amount of a non-liquid crystal polymer, relative to inflatable members produced from only thermoplastics such as PET.
Therefore, what has been needed is a catheter with an inflatable member having improved strength characteristics. The present invention satisfies these and other needs.